Although there may be more, there are generally at least two primary types of cardiac conduction devices (CCDs). Those two primary types of CCDs are mechanical pacemakers and implantable cardioverter defibrillators. A mechanical pacemaker is an electronic device that produces small bursts of electrical energy to the heart, when needed, to increase the heart beat during period(s) when the heart's natural electrical activity is slower than desirable. Alternatively, implantable cardioverter-defibrillators stop dangerously rapid heart rhythms by delivering a large electric shock to the heart to prevent cardiac arrest.
The mechanical pacemaker typically includes a power source and circuitry configured to send timed electrical pulses to the lead. The lead carries the electrical pulse to the heart to initiate a heartbeat, and transmits information about the heart's electrical activity to the pacemaker. The lead can include a fixation mechanism that holds the lead to the cardiac tissue. In some cases, a lead is inserted through a vein or artery (collectively vasculature) and guided to the heart where it is attached. In other instances, a lead is attached to the outside of the heart.
Implantable cardioverter-defibrillators typically include particular types of coils that provide the electric shock. The leads are generally placed within the region of the brachiocephalic vein-superior vena cava junction and in the right ventricle positioned so that the shock coils are located in the region of the brachiocephalic vein-superior vena cava junction and in the right ventricle. An implantable cardioverter-defibrillator is capable of sensing the heart's rhythm, and in the event it senses a particular type of rhythm, such as tachyarrhythmia, the implantable cardioverter-defibrillators sends a relatively large shock to the heart.
For the mechanical pacemakers and CCDs to work effectively, the leads are preferably in contact with heart tissue. For example, a lead for a CCD typically passes through a vein under the collarbone to the innominate vein, past the superior vena cava (“SVC”), and into the right atrium of the heart. The distal portion of the lead then enters the right ventricle and attaches to the heart via a fixation mechanism, such as a small screw and/or hooks at the end. In certain instances, a lead may be attached to the outside of the heart.
Within a relatively short time after a lead is implanted into the body, the body's natural healing process may cause tissue to form around the lead, thereby encasing it. Although leads are designed to be implanted permanently in the body, occasionally these leads must be removed, or extracted. Leads may be removed from patients for numerous reasons, including but not limited to, infections, lead age, and lead malfunction. Accordingly, removal or extraction of the lead may present associated complications.
A variety of tools have been developed to make lead extraction safer and more successful. Current lead extraction techniques include mechanical traction, mechanical cutting devices, and laser devices. Mechanical traction may be accomplished by inserting a locking stylet into the hollow portion of the lead and then pulling the lead to remove it. The mechanical cutting devices and laser devices generally include a coring technique, which includes cutting or ablating the tissue from and/or around the lead.
Further complicating lead removal is the fact that in some cases, the leads may be located in, and/or attached to, the body of a patient in a structurally-weak portion of the vasculature. For instance, typical leads in a human may pass through the innominate vein, past the SVC, and into the right atrium of the heart. A majority of tissue growth can occur along the SVC and other locations along the innominate vein where the leads make contact with the vein walls. However, tissue growth can also occur at locations within a patient where the leads make contact with arterials or other areas of the vasculature. Certain veins and arteries, and certain areas of vein and arterial walls, can be thin which can make lead removal a complicated and delicate process.